A compound with a molecular formula of C$_{10}$H$_{12}$O gives the following $^1$H NMR data:
$^1$H NMR (400 MHz, CDCl$_3$): $\delta$ 7.38-7.20 (m, 5H), 2.97 (t, J = 7.5 Hz, 2H), 2.84 (t, J = 7.8 Hz, 2H), 2.21 (s, 3H). a) What is the degree of unsaturation of the compound?
b) What is its structure?
Which hydrogens are responsible for the multiplet at $\delta$ 7.38-7.20?
c) What characteristic of these hydrogens makes them show up so far downfield?